Synthetic corn hybrid P67

ABSTRACT

A synthetic hybrid corn plant having the designation P67, produced by crossing two proprietary Optimum Quality Grain, L.L.C. maize synthetics, P53.1A-Reid and P41.1B-Lancaster. P67 has the unique property of imparting high oil levels in the grain of certain normal and male sterile hybrids when used as a pollinator. P67 is characterized by excellent cold tolerant seedling vigor for rapid emergence in cold soils and excellent early-season adaptability facilitating nicking with early maize hybrids to condition fast dry-down and superior grain quality in the grain arising from the recipient female grain parent. This invention thus relates to the seeds, plants and plant parts of P67, to plants regenerated from tissue culture of the plants or plant parts of P67, to a method of producing P67, and to a method for producing grain using P67 as a pollinator.

FIELD OF THE INVENTION

This invention is in the field of plant breeding. Specifically, thisinvention relates to a novel synthetic corn hybrid having thedesignation P67 and useful in the proprietary TOPCROSS® grain productionsystem described in U.S. Pat. Nos. 5,704,160 and 5,706,603 by Bergquistet al.

BACKGROUND OF THE INVENTION

Uses Of Corn

Corn (Zea mays L.) is an important crop used as a human food source,animal feed, and as a raw material in industry. The food uses of corn,in addition to the human consumption of corn kernels, include productsof both the dry milling and wet milling industries. The principalproducts of dry milling include grits, meal and flour. The principalproducts of wet milling include starch, syrups, and dextrose. A byproduct of both dry and wet milling is corn oil, which is recovered fromcorn germ. As animal feed, corn is used primarily as a feedstock forbeef cattle, dairy cattle, swine, poultry, and fish.

Industrial uses of corn mainly consist of the use of corn starchproduced by wet milling and corn flour produced by dry milling and thewhole kernel fermentation for production of food-grade and industrialuse ethanol. The industrial applications of corn starch and flour arebased on their functional properties, such as viscosity, film formationability, adhesiveness, absorbent properties and ability to suspendparticles. Corn starch and flour are used in the paper and textileindustries, and as components in adhesives, building materials, foundrybinders, laundry starches, sanitary diapers, seed treatments,explosives, and oil-well muds. Plant parts other than the corn kernelsare also used in industry. For example, stalks and husks can be madeinto paper and wallboard, and corn cobs can be used for fuel and to makecharcoal.

Principles of Conventional Plant Breeding

Virtually all of the commercial corn produced in the United States isproduced from hybrid seed. The production of hybrid seed first requiresthe development of elite corn inbred lines that possess good combiningability to produce agronomically superior hybrids. The majority ofhybrid seed produced in the United States is of the single cross type,wherein two inbred lines are intermated, or crossed, to produce what istermed an F₁ single cross hybrid. The resulting kernels from thisintermating are then sold as seed to commercial growers who plant theseed and harvest the second generation, or F₂ grain, for use on farm orfor commercial sale.

The production of a conventional single cross hybrid seed involvescontrolling the direction of pollination from one inbred to the other toassure the production of predominantly hybrid (cross pollinated) seed.Typically directed pollination is accomplished by interplanting separaterows of female corn plants with male corn plants. The female corn plantsthat are male sterile may be produced by genetic mechanisms which renderthe corn tassel nonfunctional or by detasseling the plants in the field.

The development of corn hybrids requires the development of homozygousinbred lines or uniform synthetic populations of unique heteroticbackground, the crossing of these lines or synthetic populations, andevaluation of test crosses. Pedigree breeding and recurrent selectionbreeding programs are used to develop inbred lines and syntheticpopulations from breeding populations. Breeding programs combinedesirable traits from two or more inbred lines or various broad-basedsources into breeding pools from which new inbred lines or syntheticpopulations are developed by inbreeding or random mating and selectionof desired phenotypes. The new inbreds and/or synthetic lines arecrossed with other inbred lines and/or synthetic populations and thehybrids from these crosses are evaluated to determine which havecommercial value and agronomic usefulness.

Pedigree breeding starts with the crossing of two genotypes, each ofwhich may have one or more desirable characteristics that is lacking inthe other or which complements the other. If the two original genotypesdo not provide all of the desired characteristics, other sources can beincluded during the breeding. In the pedigree breeding method, superiorplants are selfed or random mated and the resulting seed selected insuccessive generations. Pedigree records of ancestry are carefullymaintained for each family and ear row selection through succeedinggenerations. In the succeeding generations, the heterozygous conditionof the corn germplasm gives way to homozygous true breeding lines as aresult of inbreeding and selection. Typically in the pedigree method ofbreeding, five or more generations of inbreeding and selection ispracticed: F₁ to F₂; F₂ to F₃; F₃ to F₄; F₄ to F₅, etc.

Backcrossing can be used to improve an inbred line by transferring aspecific desirable trait from one inbred or source to another inbredthat lacks that trait. This can be accomplished, for example, by firstcrossing a superior inbred (recurrent parent) to a donor inbred(nonrecurrent parent). The donor inbred carries (donates) theappropriate gene(s) for the desired trait to the next generation. Afterfive or more backcross generations with selection for the desired trait,the inbred will be heterozygous for loci controlling the characteristicbeing transferred, but will be like the superior parent for most oralmost all other genes. The last backcross generation can be selfed toproduce a pure breeding progeny for the gene(s) being transferred.

An important consequence of the homozygosity and homogeneity of theinbred lines is that the hybrid between any two inbreds will always bethe same. Once the inbreds or synthetics that give the best hybrid havebeen identified, the hybrid seed can be reproduced indefinitely as longas the homogeneity of the inbred or synthetic parents is maintained.

A synthetic hybrid consists of an array of similar genotypes that wereidentified from intercross tests and bulked into a random matingpopulation having a desired phenotype. The intercrosses between twodifferent heterotic groups results in the continuous production of aspecific synthetic hybrid of desired phenotype.

As previously noted, a single cross hybrid is produced when twounrelated inbred or synthetic lines are crossed to produce the F₁progeny. A three-way cross hybrid is produced from three inbred lines(or synthetics) where two of the inbred lines (or synthetics) arecrossed (A×B) and then the resulting F₁ hybrid is crossed with the thirdinbred (or synthetics) (A×B)XC. A double cross hybrid is produced fromfour inbred lines (or synthetics) by crossing pairs (A×B) and (C×D) andthen crossing the two F₁ hybrids (A×B)×(C×D).

Much of the hybrid vigor exhibited by F₁ hybrids is lost in the nextgeneration (F₂). Consequently, seed (grain) from hybrid varieties is notused for planting stock.

The objective of typical plant breeding is to combine in a singlevariety/hybrid the desirable traits of the parental lines. For fieldcrops such as corn, these desirable traits may include resistance todiseases, insects, herbicide tolerance, and tolerance to heat anddrought, reducing time to crop maturity, and improved agronomic quality.With mechanical harvesting of many crops, uniformity of plantcharacteristics such as germination time and stand establishment, growthrate, and fruit/seed size are also desirable.

The problem with conventional breeding techniques is that there areseveral grain quality traits, such as high oil content, that cannotreadily be combined in a high-yielding single cross hybrid. By contrast,synthetic hybrids, such as the one described herein, when used as apollinator in the TOPCROSS® grain production system, can impartdesirable grain quality characteristics, such as high oil content, tothe resulting F₁ grain without significant loss of yield.

Synthetic Varieties

Corn has male flowers, located on the tassel, and female flowers,located on the ear, of the same plant. Because of this monoecy, cornplants can be bred by both self-pollination and cross-pollinationtechniques. Corn is self-pollinated if pollen from one flower istransferred to the same or another flower on the same plant. Corn iscross-pollinated if the pollen comes from a flower on a different plant.

Plants that have been self-pollinated and selected for uniform type overmany generations become homozygous at almost all gene loci and produce auniform population of true breeding progeny. Cross pollination betweentwo homozygous lines produces a uniform population of hybrid plants thatnevertheless may be heterozygous for many gene loci. A cross between twoplants that are each heterozygous for a number of gene loci will producea population of hybrid plants that differ genetically and will not beuniform.

Natural pollination occurs when wind blows pollen from tassels to silksthat protrude from tops of the incipient ears on plants of the samegenotype and different genotype, resulting in both self- andcross-pollination. When a population of genotypes are combined from allpossible intercrosses among a number of selected genotypes and areallowed to open pollinate, the result is called a synthetic variety. Asynthetic variety is made up of genotypes which previously have beentested for their ability to produce a superior progeny when crossed inall combinations.

Corn plants may be maintained as an outcrossing synthetic populationthat is much less homogeneous than a self-pollinated group. Every plantin such a group is certain to be heterozygous at many or most loci, andthis heterozygosity must either be maintained during a breeding programor restored at the end of the program, if productivity is to besatisfactory. The main requirement in maintaining a synthetic line isthat a sufficient number of plants of heterozygous background bemaintained to recover the gene frequencies that are desired for thesynthetic population so as to prevent genetic drift toward undesiredgene frequencies.

The Desirability of High Oil Content Grain

The concentration of oil in most varieties of corn ranges from less than3.0 percent to 4.5 percent at 0% moisture. Embryos of ordinary corn cancontain 30 percent oil, while embryos of high oil corn strains cancontain as much as 50 percent oil and are much larger in size thanordinary corn embryos.

There are several reasons for wanting to develop a method for growingcorn that is high in oil content. First, corn oil is a premium oil andregularly more valuable than starch, the other major component of cornkernels. Second, high oil corn possesses a higher available energycontent than ordinary corn, and thus is a more valuable feed for poultryand livestock. In animal feeding trials it has been found that less highoil corn is required per unit of gain than is required with ordinarycorn. In addition, high oil corn requires substantially less soybeanmeal to balance a typical animal diet, and may be used to replace oilcontaining additives in animal feed.

Additional impetus was given to breeding corn for high oil by thedevelopment of wide-line nuclear magnetic resonance spectroscopy (NMR)and near-infrared spectroscopy (NIR) as analytical tools for thenondestructive analysis of bulk or single kernel samples that can becarried out in as little as two seconds. The development of such toolsmade it much easier and much quicker to determine the oil content ofgrain, thereby encouraging experimentation in the area of breeding forhigh oil.

Thus there exists at present a growing market for corn having high oil,increased protein and other special end-use properties which is not metby corn of standard composition. The diverse types of corn available toplant breeders provides a potential for modification of quality andquantity of grain protein, starch, and oil. Corn now can be developed tomore precisely meet the specific nutritional requirements of animals orto meet particular industrial needs.

The TOPCROSS® Grain Production System

Unfortunately, high oil is a property that cannot readily be achieved ina high yielding single-cross hybrid. This is because oil content, whilebeing a moderately heritable trait, is influenced by a series of oilgenes that have additive effects on oil content and occur at a complexof loci in at least eight linkage groups that influence the amount ofoil in the grain progeny. obtaining a hybrid having all or most of theseoil genes can take many years of breeding. Further increasing thedifficulty of breeding for high oil content is the fact that the grainyield of higher oil hybrids is generally inferior when compared to elitedent corn hybrids.

A method of producing a high yield of corn having high oil contentwithout requiring years of breeding is described in Bergquist et al.U.S. Pat. No. 5,704,160. The primary aspect of this method, known as theTOPCROSS® grain production system, is the interplanting of a pollinatorcorn plant possessing the characteristics for significantly increasingoil and protein levels in the resulting grain with a male sterile hybridcorn plant. The resulting grain possesses an oil content much higherthan would be expected for self- or cross-pollination of the fertileversion of the hybrid corn plant.

In practice, the seed of the pollinator with improved grain qualitytraits is blended in small amounts with seed of an elite male sterilegrain parent hybrid, but with sufficient pollinator seed to permitabundant pollen production for fertilization of the male sterile grainparent hybrid. The relatively low ratio of pollinator seed to malesterile grain parent seed (less than one pollinator plant to every threegrain parent plants) takes advantage of the higher grain yield potentialof the elite grain parent hybrid while assuring a sufficient populationof pollinator plants to pollinate the male sterile grain parent plants.

Need for Superior Pollinators

Critical to the success of the TOPCROSS® grain production system is theuse of a pollinator capable of enhancing the grain quality traits of theF₁ offspring. To obtain such pollinators, the corn breeder must selectand develop corn plants that have the traits that result in superiorinbred and synthetic parental lines.

The pollinator for the TOPCROSS® grain production system need not begenetically homozygous (inbred) or even uniform in appearance, and neednot be selected for genetic combining ability with female plants.However, the pollinator should have uniform desirable grain qualitycharacteristics, such as high oil, that will influence the grain qualitycharacteristics of the F₁ offspring, and the ability to pollinate thefemale plants. A hybrid obtained by crossing two synthetic populationsof different heterotic backgrounds results in a synthetic hybrid withpredictable heterozygosity and genetic variability among plants that isparticularly useful as a male pollinator in blends with male sterilehybrid grain parents in the TOPCROSS® grain production system. Somegenetic variability is desirable because it extends the flowering periodof the pollinator. P67 was developed to achieve these characteristics.

Advantages of Synthetic Hybrids

The use of synthetic hybrids (such as P67) as TOPCROSS® grain productionsystem pollinators affords a number of advantages over the use ofinbreds, hybrids produced from single crosses, or hybrids produced fromthree way crosses. For instance, synthetic hybrids can be developed morerapidly than commercial hybrids. Specifically, the use of a syntheticpopulation can more rapidly establish stability of dominant oil genes,thus by-passing the many generations of inbreeding that is required toproduce inbreds for making single cross hybrids.

Second, synthetic hybrids often have excellent vigor comparable to thatof commercial hybrids. Inbreds, by contrast, typically lose vigor witheach successive generation of inbreeding. This is an important advantageof synthetics because pollinator vigor is critical for ample pollen shedat the time of silking in the TOPCROSS® grain production system.Synthetic hybrid P67 expresses cold vigor in seedling growth stagesgreater than even most open pollinated synthetic populations.

Third, a synthetic variety, utilizing heterosis in which pollinationcontrol is a factor, is more likely to disperse pollen over a longerperiod of time than a single cross hybrid. The predictable greatervariability of synthetic varieties as compared with single crossespermits more flexibility to meet the changing growing conditions typicalof field production. In addition, because of the longer floweringperiod, fewer synthetic pollinators need be developed to be used inblends with many different grain parents.

Fourth, the synthetic hybrid pollinator is more easily produced duringperiods of heat and drought stress on dryland production than asingle-cross hybrid using less vigorous inbred seed stocks. For example,in non-irrigated dryland field tests conducted during 1993 and 1994,production of synthetic hybrid seed remained relatively constant atabout 55 bushels per acre despite the fact that rainfall accumulationduring the critical months of May, June and July fell from 40.84 cm in1993 to 13.82 cm in 1994. Over the same period, single cross seedproduction using inbred seed stocks fell to less than 25 bushels peracre in 1994 from 55 bushels per acre in 1993.

Fifth, the single cross synthetic hybrid pollinator which results fromthe cross of two parental synthetic populations, A×B, is more quicklyproduced in a single generation compared to a three-way cross pollinator(A×B)C that requires an additional plant generation to produce thehybrid three-way cross pollinator. For example, the A×B synthetic hybridis simply produced in a single plant growing generation in theproduction of P67 single-cross synthetic hybrid while the three-waycross synthetic hybrid pollinator would require an additional plantgeneration to produce the final hybrid (A×B) crossed to the parentalC-population to produce a synthetic three-way hybrid cross designated(A×B)C.

SUMMARY

According to the invention, there is provided a novel synthetic cornhybrid, designated P67, that when used to pollinate an elite malesterile hybrid grain parent, produces commercial grain exhibitingimproved quality grain traits, including high oil. Furthermore, when P67is used to pollinate male sterile hybrid grain parents that areharvested as whole plants at approximately 50% plant moisture, itproduces commercial fodder that expresses improved feeding qualitytraits, including improved efficiency and rate of weight gain.

P67 is characterized by excellent cold tolerant seedling vigor for rapidemergence in cold soils and excellent early-season adaptabilityfacilitating nicking with early maize hybrids to condition fast dry-downand superior grain quality in the grain arising from the recipientfemale grain parent.

This invention thus relates to the seeds, plants and plant parts of P67,to plants regenerated from tissue culture of the plants or plant partsof P67, to a method of producing P67 by crossing P53.1A and P41.1Bsynthetics, and to a method for producing grain using P67 as apollinator.

DEFINITIONS

In the description and examples that follow, a number of terms are used.In order to provide a clear and consistent understanding of thespecification and claims, including the scope to be given such terms,the following definitions are provided:

Backcross. The cross of a hybrid to either one of its parents. Theoffspring of such a cross is referred to as the backcross generation.

Backcross Method of Breeding. A system of breeding carried out byseveral generations of backcrossing to one of the parents of a hybridand subsequent selection. The characteristics of the recurrent parentare retained for the most part, and characteristics from thenonrecurrent parent are added.

Bulk Method of Breeding. The growing of segregating generations of ahybrid of self-pollinating crops in a bulk, with or without massselection, followed by individual plant selection in F₆ or latergenerations.

Cytoplasmic Inheritance. Transmission of hereditary characteristicsthrough the cytoplasm as distinct from transmission by genes carried bychromosomes in the nucleus. Detected by differing contribution of maleand female parents in reciprocal crosses.

Donor Parent. The parent from which one or a few genes are transferredto the recurrent parent in backcross breeding.

Ear Height. The ear height is a measure from the ground to the topdeveloped ear node attachment and is measured in centimeters.

Early Stand Count. This is a measure of the stand establishment in thespring and represents the number of plants that emerge on a per-plotbasis for the hybrid.

Elite. This term characterizes a plant or variety possessing favorabletraits, such as, but not limited to, high yield, good grain quality anddisease resistance.

Embryo. The rudimentary plant in a seed. The embryo arises from thezygote. In high oil corn breeding, increases in oil content areaccompanied by increases in embryo size.

Endosperm. The nutritive tissue formed within the embryo sac in seedplants. It commonly arises following the fertilization of the twoprimary endosperm nuclei of the embryo sac by the two male sperms. In adiploid organism the endosperm is triploid.

Expressivity. The degree of manifestation of a genetic character.

F₁. The first generation of a cross.

F₂. The second filial generation obtained by self-fertilization orcrossing inter se of F₁ individuals.

F₃. Progeny obtained by self-fertilizing F₂ individuals. Subsequentgenerations F₄, F₅, etc.

Field Corn. Varieties or cultivars of corn grown extensively on largeacreage within a broad but defined geographic area for the production ofgrain and/or forage.

GDD Shed. The GDD is the number of growing degree days (GDD) or heatunits required for an inbred line or hybrid to reach anthesis or pollenshed from the time of planting. Growing degree days are calculated bythe Barger Method, where the heat units for a 24-hour period are:${GDD} = {\frac{\left( {\text{Max.} + \text{Min.}} \right)}{2} - 50}$

The highest maximum used is 86 degrees F. and the lowest minimum used is50 degrees F. For each hybrid it takes a certain number of GDDs to reachvarious stages of plant development. GDDs are a way of measuring plantmaturity.

General Combining Ability. The average or overall performance of agenetic strain in a series of crosses.

Genotype. The fundamental genetic constitution of an organism.

Germ. The embryo of the corn kernel. It contains most of the oil foundin the kernel.

Grain. Comprises mature corn kernels produced by commercial growers forpurposes other than growing or reproducing the species.

Grain Parent. Male sterile, elite hybrid that comprises a large majorityof the plants in the TOPCROSS® grain production system.

Grain Parent Seed. Corn seed used to produce grain parent plants.

Grain Quality Trait. This is any attribute of grain that is ofcommercial value. Such traits relate to the intermediate or final use ofgrain and include but are limited to the quantity or quality of oil,protein, starch, pigmentation, and fiber found in corn grain. Suchtraits also encompass physical attributes of the grain itself, such asgrain texture, size, or hardness, among others. Certain of thesecompositional or physical attributes of grain correlate with functionalattributes as well which are of commercial importance, such assusceptibility to breakage and spoilage, among others.

Heterozygous. A genetic condition existing when different alleles resideat corresponding loci on homologous chromosomes.

High Oil Source. A population of corn plants containing high oil genesused for corn breeding.

Homozygous. A genetic condition existing when identical alleles resideat corresponding loci on homologous chromosomes.

Hybrid. (1) The progeny of a cross fertilization between parentsbelonging to different genotypes. (2) The first generation offspring ofa cross between two individuals differing in one or more genes.

Hybrid Vigor. The phenomenon in which the cross of two stocks producehybrids that show increased vigor-heterosis compared to the parentstocks.

Inbred. A substantially homozygous individual, variety or line.

Inbred Line. (1) A line produced by continued inbreeding. In plantbreeding a nearly homozygous line usually originating by continuedself-fertilization, accompanied by selection. (2) A relativelyhomozygous line produced by inbreeding and selection.

Kernel. The corn caryopsis comprising a mature embryo and endospermwhich are products of double fertilization.

Line. A group of individuals from a common ancestry. A more narrowlydefined group than a variety.

Male Sterility. A condition in which pollen is absent or non-functionalin flowering plants.

MN RM. This represents the Minnesota Relative Maturity Rating (MN RM)for the hybrid and is based on the harvest moisture of the grainrelative to a standard set of checks of previously determined MN RMrating. Regression analysis is used to compute this rating.

Moisture. The moisture is the actual percentage moisture of the grain atharvest.

Ovule. A structure consisting of female reproductive tissue surroundedby maternal tissue.

Pedigree. A record of the ancestry of an individual, family, or strain.

Pedigree Breeding. A system of breeding in which individual plants areselected in the segregating generations from a cross on the basis oftheir desirability and on the basis of a pedigree record.

Percent Oil. The oil concentration of a corn kernel expressed on a dryweight basis.

Percent Yield. The yield obtained for a hybrid in terms of percent ofthe mean for the experiments in which it was grown.

Phenotype. (1) Physical or external appearance of an organism ascontrasted with its genetic constitution (=genotype). (2) A group oforganisms with similar physical or external makeup. (3) The observedcharacter of an individual without reference to its genetic nature.

Plant Height. This is a measure of the height of the hybrid from theground to the tip of the tassel and is measured in centimeters. The datais given in percentage of mean of the experiments in which the hybridwas grown.

Polar Nuclei. Found in the ovule to give rise to the embryo andendosperm of the mature corn kernel.

Pollen. A structure which contains the two haploid sperm nuclei whichfuse with the egg nucleus and polar nuclei found in the ovule to giverise to the embryo and endosperm of the mature corn kernel.

Pollinators. Male fertile corn plants that are used to pollinate malesterile hybrid corn plants.

Pollinator Seed. Corn seed that, when sown, germinates to producepollinator plants.

Population. In genetics, a community of individuals which share a commongene pool. In statistics, a hypothetical and infinitely large series ofpotential observations among which observations actually made constitutea sample.

Recurrent Parent. Used in backcrosses to refer to the parent to whichthe first cross and successive backcrossed plants are crossed.

Seed. Mature corn kernels produced for the purpose of propagating thespecies.

Seed parent. A corn line that is pollinated by pollen from pollinatorplants, with hybrid corn seed resulting from this pollination.

Seedling Vigor. This is the visual rating (1 to 5) of the amount ofvegetative growth after emergence at the seedling stage (approximatelyfive leaves). A higher score indicates better vigor.

Stay Green. Stay green is the measure of plant health near the time ofblack layer formation (physiological maturity). A low score on a scaleof 1 to 5 indicates better late-season plant health.

Synthetic Hybrid. Any offspring of a cross between two geneticallyunlike synthetic individuals or unlike individuals.

Synthetic Population. A genetically heterogeneous collection of plantsof known ancestry created by the intermating of any combination ofinbreds, hybrids, varieties, populations, races or synthetics.

Synthetic Variety. A variety produced by crossing inter se a number ofgenotypes selected for good combining ability in all possible hybridcombinations, with subsequent maintenance of the variety by openpollination.

Test Cross. A cross of a double or multiple heterozygote to thecorresponding multiple recessive to test for homozygosity or linkage.

Test Weight. The measure of the weight of the grain in pounds for agiven volume (eg. bushel), adjusted for percent moisture.

TC BLEND®. A trademark of E.I. du Pont de Nemours and Company for cornseed for agricultural purposes.

TOPCROSS®. A trademark of E.I. du Pont de Nemours and Company for highoil corn seed.

TOPCROSS® Grain Production System. A method of commercial cornproduction whereby a low yielding male fertile corn pollinator isblended at 8 to 20 percent of the total seed count with an elite highyielding male sterile hybrid grain parent and allowed to pollinate themale sterile grain parent to produce grain having increased food andfeed nutritional value, thus capitalizing on the high yield potential ofthe male sterile hybrid grain parent while contributing the grainquality traits from the fertile pollinator.

Variety. A subdivision of a species. A group of individuals within aspecies which are distinct in form or function from other similar arraysof individuals.

Yield (Bushels/Acre). The yield in bushels/acre is the actual yield ofthe grain at harvest adjusted to 15.5% moisture.

DETAILED DESCRIPTION OF THE INVENTION

P67 is a yellow dent corn, high oil single cross synthetic hybrid havingsuperior agronomic characteristics and the ability to impart desirablegrain quality traits to a first generation grain when used as apollinator in the TOPCROSS® grain production system.

Synthetic hybrid P67 is produced by planting synthetic populationsP53.1A-wx and P41.1B, allowing one synthetic to pollinate the other, andharvesting the resulting seed. Either synthetic parental population maybe used as female parent or the male parent. Preferably, syntheticP53.1A-wx is the female of the cross and synthetic P41.1B is the male ofthe cross because of the larger seed size grade-out resulting from the53.1A-wx seed parent in hybrid synthetic production. Production plantingof the male and female synthetics can be made at the same time due tothe fact that male pollen is shed at the same time the female silks arereceptive to the pollen.

P53.1A-wx and P41.1B were produced by conducting a series of crosses,selfings and backcrosses beginning with the crossing of LH51 with ASKC28(for P41.1B) and the crossing of LH132 and B73 with ASKC28 and B73 withUHOC3 (for P53.1A-wx). During the random mating generation ofdevelopment of P53.1A-wx and P41.1B, test crosses were made to a hybridgrain parent tester and the resulting grain was analyzed to identifynormal grain type segregate with favorable dominant oil genes expressinghigh oil in the genetic segregants.

When produced according to the method disclosed herein, both P53.1A-wxand P41.1B breed true, that is, produce a P67 synthetic hybrid that isboth reproducible and usable as a high oil pollinator in the TOPCROSS®grain production system.

Characteristics of P67

Synthetic corn hybrid P67 most closely resembles maize synthetics P39and P41 in maturity and usage, and ASKC28, UHO and ASKC20 incharacteristics of plant type, ear type and kernel type. P67 expressesmoderately higher grain test weight than ASKC28, UHO and ASKC20 withnormal grain and dent phenotype that expresses a moderately soft starch.

P67 synthetic hybrid has the following characteristics, based on dataprimarily collected at Applicant's El Paso, Ill. research facility(numerical values given are averages taken across a fifty plant sample):

TABLE 1 SYNTHETIC HYBRID P67 DESCRIPTION INFORMATION Type: Dent/High OilRegion Best Adapted: Most Northern, Central and Northeastern Regions ofUSA Cornbelt A. Maturity: Zone 1-2 Synthetic Maize Hybrid: P67 HeatUnits from Emergence to Shed: 1036 GDD (1998) Heat Units from Emergenceto Silk: 1082 GDD (1998) Heat Units from 50% Silk to 25% KernelMoisture: 1305 GDD (1998) Heat Units from Emergence to 25% KernelMoisture: 2365 GDD (1998) No. Reps.: 8 Where Heat Units* = [(Max. Temp.(<86 Degrees F.) + Min. Temp. (>50 Degrees F.))/2] − 50 *If Max. Temp.is greater than 86 degrees Fahrenheit, then 86 is used and if Min. Temp.is less than 50, then 50 is used. Heat units accumulated daily and cannot be less than 0. B. Plant Characteristics: Height (to tassel tip):211 cm Length of Top Ear Internode: 16 cm Number of Ears per Stalk:Slight two-ear tendency Ear Height (to base of top ear): 64 cm Number ofTillers: None Cytoplasm Type: Normal Brace Root Color: Green Number ofBrace Root Nodes: Slight two-node tendency Number of Brace Roots: 19Stalk: Straight C. Leaf: Color: Green Stalk Color: Green Angle fromStalk: 57 Degrees Attitude of Blade: Slightly curved Marginal Waves(number): 2-3 few Number of Leaves (mature plants): 12 SheathPubescence: Smooth, segregating for smooth and pubescence Color ofSheath: Pale green Longitudinal Creases: Absent Length (Ear node leaf):73 cm Width (widest point, ear node leaf): 10 cm Coleoptile SheathColor: Green First Leaf, Shape of Tip Round D. Tassel: Attitude ofLateral Branches: Mostly straight, segregating curved Number LateralBranches: 14 Branch Angle from central spike: 49 degrees Length of MainAxis Above Lowest Branch: 41 cm Length (from flag leaf): 52 cm PeduncleLength (flag leaf to basal branches): 10 cm Anther Color: Yellow GlumeColor: Green Density of Spikelets: Medium E. Ear (Husked Ear Data ExceptWhen Stated Otherwise): Length: 18 cm Weight (dried to 15.5% grainmoisture): 166 gm Mid-point Diameter: 4 cm Silk Color (at silking): Palegreen Husk Extension (Harvest stage): Short, 6 cm (ear tip occasionallyexposed) Husk Leaf (number): 7 Husk Leaf Length: 7 cm Number of Husks:12 Taper of Ear: Average taper Position at Dry Husk Stage: UprightKernel Rows: 18; Distinct, straight Husk Color (fresh): Light green HuskColor (dry): Buff Shank Length: 19 cm long Shank (No. of internodes): 10Drying Time (unhusked ear): Average Husk Length: 29 cm Husk Width: 16 cmHusk Area: 480 cm² F. Kernel (dried, size from ear mid-point): Length:12 mm Width: 7 mm Thickness: 4 mm Shape Grade (% rounds): 26%(±3%) basedon parent test Pericarp Color: Colorless Aleurone Color: Homozygous;yellow Cap Color: Yellow Endosperm Color: Yellow Endosperm Starch Type:Normal/waxy (i.e. amylopectin) starch, heterozygous for wx-gene GmWt/100 Seeds (unsized): 22 gm Test Weight: 58 lbs./bu. Percent Oil: 17.7percent (1998) Percent Protein: 14.6 percent (1998) Percent Starch: 49percent (1998) G. Cob (dried, size from ear mid-point): Diameter atmid-point: 26 mm Strength: Strong Color: Red, segregating for white andred cob color but was heterozygous for red H. Diseases: Northern LeafBlight: Intermediate Goss's Bacterial Wilt: Intermediate Southern CornLeaf Blight: Susceptible Heat Smut: Susceptible Common Smut: ResistantStewart's Bacterial Wilt: Intermediate Corn Lethal Necrosis: SusceptibleNorthern Leaf Spot: Intermediate Common Northern Rust: IntermediateSouthern Rust: Susceptible Eye Spot: Intermediate Gray Leaf Spot:Susceptible Fusarium Ear Rot: Resistant Fusarium Stalk Rot: IntermediateDiplodia Ear Rot: Susceptible Diplodia Stalk Rot: Intermediate MDMV:Susceptible Stunt: Susceptible Stay Green: Intermediate I. Insects:European Corn Borer: Susceptible J. Variety most closely resembling P67:Character Synthetic Hybrid, Hybrid, and/or Inbred Maturity P39, P41,Pfister Hybrid 2020 Plant Type ASKC28, UHO, ASKC20, P39, P53 Ear TypeASKC28, UHO, ASKC20, P39, P53 Kernel Type UHO, ASKC20, ASKC28 Usage P39,P41

P67 is adapted over a wide area of the northern corn belt and can beused advantageously as a pollinator in seed blends with male sterilehybrids from approximately 95-100 relative maturity based on theMinnesota Relative Maturity Rating System for harvest moisture of thegrain. P67 cold test vigor was excellent in laboratory tests, exhibiting93% emergence compared to 90% emergence for ASKC20, 92% emergence forUHOC3, and 83% emergence for ASKC28. Kernel size-out is also very goodfor P67, with approximately 74% of the kernels falling in the mediumflat category.

Although P67's primary use would be as a pollinator in the TOPCROSS®grain production system with blends of early maturing corn hybrid malesterile grain parents, P67 is also an acceptable male to be crossed tolater maturing full season high oil pollinators to develop mediummaturity pollinators for expanding the use of its genetics to fullerseason maturity grain parents.

Pollen production is good with P67. Under extreme heat and droughtstress, P67 may top fire and have some tassel blasting (necrosis of topleaves and tassel, respectively). P67 sheds pollen for approximatelynineteen days (Table 3) and should be blended in sufficientconcentrations (at approximately 8-10% pollinator seed to 90-92% malesterile hybrid grain parent seed) to ensure adequate pollen incommercial production of high oil corn grain where it is used as a malepollinator.

As a pollinator, P67 has shown uniformity and stability within thelimits of environmental influence for the grain traits of yield,moisture, oil concentration, protein concentration and test weight asshown in Table 2. P67 has expressed segregation for red and white cobcolor because of the genetic differences of P41.1B and P53.1A-wxsynthetic parent populations. P67 is a synthetic hybrid that has beenmaintained by hand and cross pollination in isolated fields withcontinued observation of high oil for uniformity of dominant high oilgenetics. Although segregating for cob color, glume color and plantheight in test crosses, P67 synthetic has consistently expressed highoil across different environments.

P67 is an early maturity flowering synthetic hybrid, broadly adapted tothe corn growing areas of the Northern, Central and Northeastern regionsof the United States and Southern Canada. P67 has expressed high oil andexcellent cold soil seedling vigor that conditions low grain moisture inthe grain of male sterile hybrid grain parents.

Benefits of P67 as a Pollinator

In field tests of the TOPCROSS® grain production system using P67 as thepollinator and a male sterile hybrid grain parent, P67 was found toinduce superior grain quality characteristics in grain arising on themale sterile hybrid.

In field tests, P67 and male sterile grain parent plants were allowed togrow unmolested to maturity. Both varieties were allowed to continue togrow and natural cross-pollination was allowed to occur by the action ofthe wind as is normal with most grasses, including corn. Of course, onlypollen from the fertile male parent, P67, was available for pollinationof the male sterile hybrid grain parent; the tassels, or flower bearingparts, of the grain parent having been rendered sterile bygenetic/cytoplasmic mechanisms. For convenience, the grain harvestedfrom the male sterile grain parent plants and the P67 plants willhereinafter be referred to as “high oil corn grain.”

The fields where high oil corn grain was produced were well isolatedfrom other corn fields to prevent any accidental contamination withambient pollen. Such isolation techniques may be accomplished by timeddelay with other hybrid corn production fields or by using a spacedistance pattern of more than 70 m from normal corn, well known to thoseskilled in the art of the seed corn industry.

Both the male fertile pollinator and male sterile hybrid grain parentvarieties comprising the corn seed blend were allowed to continue togrow and be harvested. The ears harvested from the male sterile grainparent expressed the higher grain yield potential of the elite malesterile grain parent and the high oil, protein and grain densityqualities of the pollen parent. The grain from the male parent syntheticvariety ears may be harvested along with the grain of male sterile grainparent hybrid for high oil corn use.

Because the same oil source (i.e. ASKC28) was used in the development ofthe P41.1B-Lancaster and P53.1A-wx-Reid parental populations, onlymodest heterotic effects for yield were expressed in P67. The low grainyields expected from synthetic hybrid P67 pollinator dictated the needfor a low percent of pollinator in the pollinator-grain parent seedblend so as to maximize yield, but a high enough percent was needed toensure sufficient pollination of the elite male sterile grain parenthybrid. Approximately eight to ten percent is preferred.

Examples of Using P67 as a Pollinator

In the examples that follow, the characteristics of high oil corn grainproduced using P67 as a pollinator are provided.

1998 Strip Test Trials

First year (1998) strip tests trials were conducted at E1 Paso, Ill.,comparing the characteristics of grain from various hybrids from PfisterHybrid Corn Company and Pioneer Hi-Bred International rendered malesterile and pollinated by P67, with characteristics of grain producedfrom grow outs of the same Pfister and Pioneer hybrids in their fertilestate (“Hybrid Self”). The hybrids used were Pioneer Hybrid P37M81 andPfister Hybrids 2020, 2025, 3034, 1400 and 1571. The results arepresented in Table 2.

TABLE 2 1998 P67 TopCross Strip Tests Results — El Paso, Illinois GrainYield-Bu/A. Moisture Percent Oil Percent Protein Percent Test Weight(lbs./bu.) % Hybrid % Hybrid % Hybrid % Hybrid % Hybrid Top- of GP Top-of GP Top- of GP Top- of GP Top- of GP Hybrid Grain Parent GDD¹ Cross GPSelf Cross GP Self Cross GP Self Cross GP Self Cross GP Self PioneerP37M81- 1055 147.6  95 155.0 14.1 104 13.6 6.97 157 4.45 10.1  103 9.856.4 100  56.6 Sdms Pfister 2020-Sdms 1085 151.9 102 148.6 18.2 121 15.08.45 187 4.51 8.6  99 8.7 53.2 94 56.8 Pfister 2025-Sdms 1105 155.4  91170.3 15.6 112 13.9 6.00 171 3.50 8.1  94 8.6 54.5 96 57.0 Pfister3034-Sdms 1189 162.8 110 147.6 21.4 106 20.1 7.59 171 4.44 8.1 100 8.153.8 96 56.3 Pfister 1400-Sdms 1189 135.0  92 146.1 15.4 108 14.2 7.42160 4.63 9.3 101 9.2 57.0 95 60.0 Pfister 1571-Sdms 1202 146.0 102 143.515.8 109 14.5 8.05 164 4.92 9.1  96 9.5 57.0 98 58.0 Overall Mean 149.8 99 151.9 16.8 110 15.2 7.41 168 4.41 8.9 100 8.9 55.3 96 57.5 ¹GDD(P67) = 1153 NOTE: “TopCross” refers to grain resulting from thepollination by P67 of both the male sterile hybrid grain parent and P67.

Traits obtained from the strip test include the following:

“Grain yield”, expressed in bushels per acre for both the grain producedby the pollination of the male sterile grain parent hybrid by P67 andthe grain produced from the grow out of the fertile hybrid.

“Moisture Percent”, expressed as a percentage of total kernel weight forboth grain produced from the pollination of the male sterile hybrid byP67 and for the grow out of the fertile hybrid. Moisture percent wasdetermined by distillation on a Brown-Duvel moisture tester manufacturedby the Seed Trade Reporting Bureau of Chicago, Ill. Electronic moisturetesters were calibrated against the moisture determinations of theBrown-Duvel moisture tester in field harvest tests.

“Oil Percent”, expressed as a percentage of the total kernel dry weightfor both grain produced from the pollination of the male sterile hybridby P67 and for the grow out of the fertile hybrid. Thus oil percent is ameasure of the content of oil in grain at harvest. Oil percent wasdetermined by NIR on a dry matter basis (0% moisture).

“Protein Percent”, expressed as a percentage of protein in the grain ona dry matter basis as determined by NIR for both grain produced from thepollination of the male sterile hybrid by P67 and for the grow out ofthe fertile hybrid.

“Test Weight”, expressed as the weight of the grain in pounds for agiven volume (bushel) adjusted for percent moisture for both grainproduced from the pollination of the male sterile hybrid by P67 and forthe grow out of the fertile hybrid.

Grain Yield Comparisons—High Oil Corn Grain Versus Hybrid Self

In the 1998 strip test trials (Table 2), blends of 8-10% pollinator seedand 90-92 percent male sterile hybrid seed were planted and grown tomaturity. Grain from both the male sterile hybrid plants and thepollinator plants was harvested.

As shown in Table 2, the overall mean yield of grain produced by thepollination of the male sterile hybrids by P67 during the first year(1998) strip tests was 99% of the overall mean yield of grain producedfrom the fertile grain parent grow outs in six comparisons.

Moisture Comparisons—High Oil Corn Grain Versus Hybrid Self

Conventional high oil hybrids traditionally express higher grainmoisture at harvest and are slower to dry down than lower-oil denthybrids of the same maturity. To test this concept of higher moistureassociated with higher oil content of grain, comparisons were made ofmoisture at harvest of grain resulting from the pollination by P67 ofthe male sterile hybrids and grain resulting from the self pollinationof the comparable fertile hybrids.

In the first year (1998) trials (Table 2), the overall mean grainmoisture at harvest from the sterile grain parent hybrids pollinated byP67 was higher than the grain moisture from the fertile grain parenthybrids alone in all six comparisons. Since higher oil content resultedin higher moisture content in all six comparisons, the first year datadid support the conventional theory regarding the relationship betweenoil content and grain moisture.

Oil Comparisons—High Oil Corn Grain Versus Hybrid Self

In the first year (1998) strip tests at El Paso, Ill., the oil contentsof grain produced from the pollination by P67 of the male sterilehybrids were compared to grain produced from the self pollination of thecomparable fertile hybrids. The results, shown in Table 2, show aconsistent increase in oil percent in the high oil corn grain comparedto the hybrid selfs. To take a couple of examples, there was about a3.9% absolute increase in oil when Pfister Hybrid 2020 was pollinated byP67 (8.45% versus 4.51%), and about a 3.1% absolute increase in oil whenPfister Hybrid 3034 was pollinated by P67 (7.59% versus 4.44%).

Protein Comparisons—High Oil Corn Grain Versus Hybrid Self

In first year (1998) strip tests (Table 2), protein content of the grainresulting from the pollination of the male sterile hybrid by P67 wascompared to the protein content of grain produced from open pollinatedfertile hybrid checks. Analysis of population means indicated that P67did not significantly increase protein in the high oil corn graincompared to the grain from the fertile grain parent check. The fact thatthe high oil corn grain did not exhibit higher protein than that of thefertile grain parent hybrid checks may have been due to a lower level ofnitrogen in the male sterile hybrid GP/P67 field.

Test Weight Comparisons—High Oil Corn Grain Versus Hybrid Self

Test weight of grain is a function of kernel density. In first yearstrip tests, comparisons were made of the test weight of grain resultingfrom the pollination by P67 of both P67 and the male sterile hybridsagainst the test weight of grain resulting from the self pollination ofthe comparable fertile hybrids. As shown in Table 2, the overall meantest weight of high oil corn grain was 55.3 lbs./Bu., or 96% of the meantest weight of the selfed hybrids (57.4 lbs./bu.).

P67 conditions a slight loss in test weight in the TopCross grain whichis reflected in a slight yield penalty. This is because P67 wasdeveloped by crossing P53.1A-wx-Reid, a soft starch grain phenotype,with P41.1B-Lancaster, a normal starch grain phenotype. This crossyields a heterogeneous condition in the P67 pollinator, i.e., thepresence of different types of male pollen gametes—soft starch andnormal starch. When P67 is used as a pollinator, the two types of malepollen gametes fertilize the male sterile hybrid grain parent. As aresult, some of the high oil corn grain expresses lower test weight(female ovules fertilized by male gametes with soft starch genotype) andthe remainder of the grain expresses normal test weight (female ovulesfertilized by male gametes with normal starch genotype). Overall, thegrain exhibits a mid-parent mean that results in a slight loss in testweight which is reflected in a slight yield penalty.

Tassel-Silk Synchronization—P67 Pollen Shed and Grain Parent SilkExtrusion

The success of the TOPCROSS® grain production system is dependent on thesynchronization of pollen shed from the pollinator with the extrusion ofsilks from the male sterile grain parent hybrid, which is termednicking.

Table 3 presents results of tassel-silk date observations and growingdegree days (GDD) to tassel shed and silk flowering for P67 pollinatorand Pfister Hybrid 2020, respectively. As shown in the table, in 1998strip tests the pollination period of P67 began July 7 and ended July25, a nineteen (19) day period. Peak pollination, i.e., the date duringwhich 50% pollen shedding was achieved, occurred on July 12 whichresulted from an accumulation of 1036 GDD. By comparison, the peak silkextrusion date for Pfister Hybrid 2020 was slightly earlier—July11—which resulted from an accumulation of 1019 GDD. These data indicatethat the nicking of pollinator P67 with male sterile Pfister Hybrid2020-Sdms is acceptable for commercial high oil corn grain production.

TABLE 3 Comparison of the Tassel Shedding Period for P67 and the SilkExtrusion Period for Pfister Hybrid 2020 Total Plants Observed — 1261998 Field Test Data July July July July July July July July July JulyJuly July July July July July July July July Date 7 8 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24 25 Percent of 2 3 13 12 13 9 16 9 13 3 2 21 2 Pollinator P67 to Start Shedding Percent of 7 3 5 13 26 8 7 15 10 11 2 2 Pollinator P67 to Stop Shedding Percent of 1 1 2 3 6 10 10 18 1211 9 8 1 4 3 1 Hybrid 2020 to Begin Silk Extrusion Growing 929 953 9771000 1019 1036 1058 1082 1103 1128 1150 1174 1201 1226 1255 1276 12971313 1329 Degree Days

Comparisons of Oil, Protein and Moisture in Grain Produced from HybridsPollinated by P67 and Self Pollinated Fertile Hybrids Harvested OverTime

Table 4 presents the oil content, protein content and moisture of grainproduced from Pfister Hybrids 2020 and 2020-Sdms (columns one and two),grain produced from Pfister Hybrids 2020 and 2020-Sdms pollinated by P67(columns three and four), and grain produced from self-pollinated P67(column five) when the grain was harvested 36 days after flowering andthen harvested on selected days to and beyond the onset of physiologicalmaturity (i.e., black-layer).

Pfister Hybrid 2020-Sdms pollinated by P67 expressed 7.7% oil content ofthe grain as early as 761 GDD after flowering, thus indicating a veryhigh level of oil while the plant foliage was green and activelygrowing. This permits an early harvest for silage and/or earlage whilemaintaining a high energy recovery from the grain.

A comparison of the protein content data shows little difference inprotein at 36 days after flowering through 65 days, suggesting thephysiological make-up of the seed is basically complete at this earlyharvest date.

A comparison of moisture over the course of 29 days (i.e., August 17 toSeptember 15) illustrates the rate of dry down. The moisture dataindicates there were no major grain moisture differences between grainresulting from the self-pollination of fertile hybrid 2020 (column one)to grain resulting from the pollination by P67 of male sterile hybrid2020-Sdms (column four) However, the rate of dry down of grain arisingon self-pollinated P67 (column five) was substantially slower that therate of dry down of grain from the self-pollinated hybrid (columns oneand two) or the hybrid pollinated by P67 (columns three and four).

TABLE 4 Percent Oil, Protein and Moisture of Grain at Harvest AcrossDays Commencing 36 Days After Pollination Through 65 Days AfterPollination of Five Corn Types (1998) Column → (1) (2) (3) (4) (5)Type(s) Pfister 2020 Pfister 2020-Sdms GDD from Planted → Pfister 2020Pfister 2020-Sdms and P67 and P67 P67 Flowering (A) (B) Oil ProteinMoist Oil Protein Moist Oil Protein Moist Oil Protein Moist Oil ProteinMoist to Harvest 8/17 (36) 4.1 9.2 49.7 4.0 10.6 49.3 9.0 9.1 48.9 7.79.2 48.7 16.5 14.8 49.5  761 8/21 (40) 4.5 8.7 42.0 4.1 9.1 44.3 7.9 8.442.7 7.7 10.7 46.1 15.5 12.5 41.5  844 8/26 (45) 4.5 9.6 34.5 4.6 8.032.9 7.6 12.3 37.5 7.7 9.9 39.7 14.2 13.6 37.4  973 8/31 (50) 4.7 8.630.4 4.2 8.3 28.6 9.1 9.5 33.6 8.7 8.6 32.9 14.6 14.9 39.4 1076 9/4 (54)4.2 9.5 27.8* 4.5 8.4 26.2* 9.1 9.1 30.0* 8.2 10.7 31.0* 13.5 11.1 32.5*1156 9/10 (60) 4.6 8.7 19.6 4.1 8.3 18.5 8.0 9.0 18.0 8.4 8.4 25.6 13.315.1 30.0 1265 9/12 (62) 25.4 1305 9/15 (65) 4.6 8.5 16.3 4.3 9.4 15.88.4 9.7 15.8 7.8 9.5 17.8 12.6 10.5 18.3 1364 MEAN 4.5 9.0 31.5 4.3 8.930.8 8.4 9.6 32.4 8.0 9.5 34.5 14.3 13.2 34.2 1093 (A) = Harvest Date(B) = Days After Pollination *Date of black layer, physiologicalmaturity.

Deposit Information

Applicant has made available to the public without restriction a depositof at least 2500 seeds of synthetic hybrid P67, at least 2500 seeds ofP41.1B-Lancaster, and at least 2500 seeds of P53.1A-Reid, with theAmerican Type Culture Collection (ATCC), Rockville, Md. 20852. Thedepositor of P67 was Optimum Quality Grains, L.L.C. The depositor ofP41.1B and P53.1A was Pfister Hybrid Corn Company of El Paso, Ill. Thedates of the deposits were Jun. 4, 1999 (for P67), Apr. 18, 1997 (forP41.1B), and Feb. 19, 1997 (for P53.1A). P67 was assigned Deposit No.PTA-173. P41.1B was assigned Deposit No. 209029. P53.1A was assignedDeposit No. 97886. The viability of the seeds was tested on Jun. 14,1999 (for P67), on May 19, 1997 (for P41.1B) and on Mar. 3, 1997 (forP53.1A). On these dates, the seeds were viable and capable ofreproduction.

The seeds deposited with the ATCC were taken from the same depositsmaintained by Optimum Quality Grains, L.L.C., Box 19, 90 North FayetteStreet, El Paso, Ill. 61738, since prior to the filing date of thisapplication. The deposits will be maintained in the ATCC depository,which is a public depository, for a period of 30 years, or 5 years afterthe most recent request, or for the enforceable life of the patent,whichever is longer, and will be replaced if they become nonviableduring that period.

Although the foregoing invention has been described in some detail byway of illustration and examples for purposes of clarity andunderstanding, it will be obvious that certain modifications andalternative embodiments of the invention are contemplated which do notdepart from the spirit and scope of the invention as defined by theforegoing teachings and appended claims.

What is claimed is:
 1. A synthetic hybrid corn seed designated P67, arepresentative sample of which has been deposited with the ATCC underDeposit No. PTA-173.
 2. A synthetic hybrid corn plant or its partsproduced by the seed of claim
 1. 3. Pollen of the synthetic hybrid cornplant of claim
 2. 4. A tissue culture comprising regenerable cells ofthe synthetic hybrid corn plant of claim
 2. 5. A corn plant regeneratedfrom the tissue culture of claim 4, wherein said plant has all thephysiological and morphological characteristics of P67.
 6. A synthetichybrid corn plant having all the physiological and morphologicalcharacteristics of the synthetic hybrid corn plant P67, Deposit No.PTA-173.
 7. A method for producing a synthetic hybrid corn seeddesignated P67, Deposit No. PTA-173, comprising the steps of: a)planting in pollinating proximity seeds of corn synthetic linesP53.1A-wx, Deposit No. 97886, and P41.1B, Deposit No. 209029; b)cultivating corn plants resulting from the planting until the time offlowering; c) emasculating the flowers of the plants of either syntheticline P53.1A-wx or P41.1B; d) allowing natural cross pollination to occurbetween the synthetic lines; and e) harvesting seeds produced on theemasculated plants of the synthetic line.
 8. A synthetic hybrid cornplant produced by crossing P67, Deposit No. PTA-173, with another,different corn plant, the resulting progeny having one half of thenuclear genotype of P67.
 9. A seed corn blend comprising a mixture ofmale sterile hybrid corn seed and the synthetic hybrid corn seed ofclaim
 1. 10. Corn grain produced by the process of: (a) planting, inpollinating proximity, seeds of synthetic hybrid corn plant P67, DepositNo. PTA-173, and seeds of a male sterile corn hybrid; (b) cultivatingcorn plants resulting from the planting; (c) allowing the P67 cornplants to pollinate the male sterile hybrid corn plants; and (d)harvesting the resulting corn grain from all plants.
 11. A syntheticcorn seed designated P41.1B, a representative sample of which has beendeposited with the ATCC under Deposit No.
 209029. 12. A corn plantproduced from a seed of claim 1 having the ability to impart desirablegrain quality traits to a first generation grain when used as apollinator in the TOPCROSS® grain production system.
 13. A corn plantproduced from a seed of claim 1 having the ability to impart a high oillevel to a first generation grain when used as a pollinator in theTOPCROSS® grain production system.
 14. A corn plant derived from a seedof claim 1 and retaining the ability to impart a high oil level to afirst generation grain when used as a pollinator in the TOPCROSS® grainproduction system.